This invention relates to an inverter stage in an integrated injection logic which includes a lateral bipolar pnp (npn) transistor and a vertical, bipolar npn (pnp) transistor which vertical transistor has at least one collector. The collector of the lateral transistor is connected with the base of the vertical transistor. The emitter of the vertical transistor is connected to one terminal of a supply voltage source, and the emitter of the lateral transistor is connected to the other terminal of the supply voltage source. A resistance is connected between the base of the lateral transistor and the said one terminal of the supply voltage source.
In order to obtain a smaller surface requirement, several doped regions in the integrated logic are used in multiple form. For instance, a part of the base-emitter junction of the vertical npn transistor is simultaneously the collector-base junction of the lateral pnp transistor connected as a current generator. Thus, a back-injection from the collector of the pnp transistor is produced in the case of a switched out vertical transistor of the preceding inverter stage, which back-injection will lower the base current of the npn transistor. Thus, a higher inverse current gain of the npn transistor is required in order to drive the latter into saturation. This is the case, in particular, since the inverse current gain decreases in the case of small currents. In order to obtain a small power dissipation, however, it is desired to work with small currents. Due to the back-injection which occurs, the noise margin is also decreased.
It is an object of the present invention to avoid the drawbacks of prior art integrated injection logic arrangements.
This objective is attained by an inverter stage of an integrated injection logic, such as the one mentioned above.
An advantage of the invention lies in the fact that the operational point of the inverter stage is changed in such a way that the inverse current gain need be only slightly above 1 during proper operation. The logic can thus be used with very small currents, and the noise margin is larger, with equal current gain.
A further advantage of the invention lies in the fact that the parasatic base currents of the npn transistor are decreased by the base resistance, and thus the inverse current gain is further increased.
Advantageously, the spread of the base-emitter chracteristics can be compensated with the help of the base resistance.
When Schottky clamping diodes are added to the collector-base junction of the npn transistor, the dynamic characteristics of the integrated injection logic are also advantageously improved.